1. Field of the Invention
This invention relates to illuminating an observed scene with electromagnetic radiation, and to imaging. It is especially, but not exclusively, concerned with projecting light in a predetermined controlled beam, and has especial, but not exclusive, applications in thermal imaging.
The invention arose in the field of thermal imaging and will be described in relation to that, but as will be appreciated it has wider applications.
2. Discussion of Prior Art
Infra thermal imagers exist and work well. To obtain good resolution pictures, for example 512×512 pixels, it is necessary to use expensive infrared cameras which now cost around £10,000 each. This limits areas where it is practical to use thermal imaging cameras.
It is an aim of at least one aspect of the invention to attempt to reduce significantly the cost of practically useful infrared (I.R.) detector arrays.
Another problem with existing thermal imaging cameras is that it can be difficult for a user to register the thermal image presented to them on a imager display (often ghostly green) and the real visible word that they can see with their normal eyesight. One example of the is that some commercial automobiles now have an infrared night driving system which has an I.R. thermal camera with good (e.g. 512×512 pixel) resolution sending signals to a visible light projector which projects a visible light representation of the I.R. scene image into a head-up display. The head up display is typically about 10 cm×10 cm and although the windscreen of the automobile is about 200 cm×50 cm some drivers have a disturbing tendency when using the I.R. imaging system to look only through the small area of the head-up display: they may not scan the full view that they can see out of the windscreen properly at night and are psychologically reduced to driving using the head-up display alone (although they are, of course, free to look beyond it if they can discipline themselves to do so). Whilst the visible representative of the I.R. image is registered on the head-up display with the visible images seen through the windscreen, the user can still have difficulties. It is an aim of one embodiment of the invention to make driving at night using an infrared system a more natural/normal experience for the driver.
Another problem is when using infrared cameras for medical imaging (for example to find veins, hot or cold spots indicative of infection or circulation problems, or to locate burns), the user (e.g. doctor or nurse) uses an infrared imager to obtain a visible light picture on an electronic display derived from I.R. information, and then may use their skill and judgement to translate that I.R. to visible light image into movements of their hands to treat the right areas of a patient's body.
It is known for a medical I.R. imager to have an I.R. camera and a visible camera and to take both an I.R. picture and a visible light picture of part of a patient and to present the user with a combined picture on an electronic display.